Boat manufacturers strive to develop boats to work for as many different situations as possible; an attempt at one boat does it all. For years, water-ski tournament boats were designed to produce as little wake as possible to cater to the slalom water ski market. The market changed and wakeboard “water-skiers” demanded boats that produced large wakes. Now with the sport of wake surfing growing, there is demand for boats that produce a larger wake at slower speeds. Also, wake surfers will want to ride on either the left or the right side of the boat. Currently, to shift from left to right requires repositioning ballast. It is likely that the people in the boat will want to do all of these activities in the same outing. Designing a boat to perform well for all these demands is difficult with current technology.
For larger ocean capable boats, a displacement hull is advantageous in that it rides deeper in the water thus riding through the waves. Displacement hulls also consume comparatively less fuel when underway, but can only attain slower boat speeds. To attain higher speeds, a planing hull is needed. Planing hulls ride higher in the water when operating at higher speeds. The disadvantage is that by riding more on the top of the waves as opposed to riding through them, planing hull boats “bounce” across wave tops and therefore the ride is not as smooth as that of a displacement hull. It would be advantageous if the boat's operator could modify a boat hull's performance during operation.
A boat hull that has an upward curved rocker towards the stern will ride deeper in the water. This is a shape frequently utilized in a displacement hull.
In order to produce a boat that produces a small wake, the hull of a boat can have a reverse rocker (a slight downward turn) near the stern of the boat. This reverse rocker creates a lifting effect on the rear of the boat, causing the rear of the boat to ride higher in the water when moving forward, thus decreasing the wake size. Most tournament ski boats incorporate this reverse rocker.
Another method for reducing the size of the boat's wake is with trim tabs. Trim tabs are plates that mount to the boat's transom, or to the hull of the boat forward of the transom, and then extend rearward from there. The front end of the trim tab is typically flush with the bottom of the boat and frequently attached by a hinge joint. The rear end of the trim tab may be fixed or adjustable up and down, typically by hydraulic linear actuators. With the trim tab in the up position, there is little or no force on the water generated by the trim tab. With the trim tab in the down position, the trim tab creates an upward force on the rear of the boat. Trim tabs increase the versatility of boats. With motor driven or hydraulic trim tabs, the boat's operator can adjust them while the boat is underway and modify the performance of the boat.
One approach to increasing the size of the boat's wake is with the use of underwater wings. These wings are “upside-down” hydrofoils that generate downward force when the boat is moving forward. One example of this downward force hydrofoil is the “Wedge” commercially available on Malibu brand tournament ski boats. Another example is U.S. Pat. No. 6,105,527 which describes the use of “upside-down” hydrofoils to enhance wake size.
Another approach to increasing the size of the boat's wake is water ballast. There is significant prior art for boat ballast such as U.S. Pat. No. 5,787,835 and U.S. Pat. No. 6,234,099. Wake surfers add a few hundred pounds of ballast, or even more; as much as 2,000 pounds. While this produces a larger wake, it reduces the performance and safety margin of the boat.
Yet another approach to increasing the size of the wake is to add wave forming protuberances to the sides of the boat as taught in U.S. Pat. No. 6,105,527. While perhaps functional, this approach is not practical as the boat would be unable to utilize existing trailers, boat lifts or typical docking facilities.
Another approach to develop a multi-functional boat hull is commercially available on some Correct Craft brand tournament ski boats. Specific Correct Craft boats have a feature called Hydro-Gate™ that is a vertically oriented plate at the center of the transom of the boat. It can be retracted out of the flow of water or extended into the flow of water passing beneath the boat. When extended into the down position, into the water, it creates a lifting force on the rear of the boat.